This invention relates to a centrifugal separator of the type comprising a centrifuge bowl around which is provided a jacket for supply of feed water to the area between the jacket and the bowl for supplying fluidizing water into the bowl and particularly to a discharge arrangement for discharging the collected materials from the bowl after processing of a batch of materials.
A centrifugal separator manufactured in accordance with a design of the present inventor is shown for example in U.S. Pat. No. 4,846,781 issued Jul. 11, 1989. In the design shown in this patent the present inventor has taken careful steps by the design of the bowl and injection of fluidizing water from the jacket into the bowl to maximize the efficiency of separation which occurs within the bowl.
One problem which has arisen in view of the design of this bowl is that of providing effective discharge of the collected material from the grooves in the bowl once a batch of material has been processed and the bowl halted. It will be appreciated that the separator of the type shown is a batch type separator in that a quantity of material is processed and the heavier or higher specific gravity materials are collected between the grooves in the bowl until the grooves are effectively filled with the separated materials. Once this occurs it is necessary to halt the processing and to wash down the material for collection at the base of the bowl.
In the design using a surrounding water jacket for the injection of fluidizing water into the bowl through openings at the base of the groove, it is difficult to provide a discharge opening. This problem arises since the water for the water jacket is supplied through the shaft which supports the bowl for rotation. The shaft is generally attached to a hub which is itself attached to the base of the water jacket and hence there is no room available for the discharge at that point. The discharge of the above design is therefore offset to one side and is located under the lowermost one of the grooves at the peripheral wall of the bowl. This location has however provided difficulties in washing down the material from the bowl in that the material tends to collect on the base and is reluctant to move to the discharge opening.
Another design of separator which uses the water jacket principle is shown in Australian application number 22055/35 of MacNicol which was published in 1936. In this arrangement, the water is supplied along the shaft supporting the bowl and is connected to the water jacket by a plurality of pipes extending from the shaft to the base of the jacket which extends only over the peripheral wall. The outlet for the discharge of the materials from the bowl is arranged as a plurality of openings at spaced positions around the hub connecting the shaft to the base of the bowl. This arrangement is completely impractical since the positioning of the openings will cause materials to be expelled from the base through those openings during normal processing without the materials passing over the separation area. Furthermore the connection of the feedwater through individual pipes is impractical due to the fact that the pipes are very vulnerable to damage and particularly to wear during the engagement of those pipes with the highly abrasive materials to be separated while the pipes are rotated about the axis at high velocity.
A separator of an entirely different kind is shown in U.S. Pat. No. 4,824,431 (McAlister) which includes no water jacket for injecting fluidizing water and uses a different shape and type of collection system on the peripheral wall. As there is no water jacket, the bowl can be open at the center of the base to release collected materials when the bowl is halted.